Reusable shielded container



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Filed May 10, 1960 Dec. 18, 1962 F. E. GALVIN ETAL 3,069,005

REUSABLE SHIELDED CONTAINER 2 Sheets-Sheet 1 L0' 09 (9' 9 LT. Ll. p Q

L: 2 2 10 u. 0' il- S m "2 v I m g f LI.- 2 m N o N g N INVENTORS FRANCIS E. GALVIN GERALD J. ROFFMAN ATTORNEYS:

FIG.I

Dec. 18, 1962 7 E. GALVIN ETAL 3,

REUSABLE SHIELDED CONTAINER Filed May 10, 1960 2 Sheets-Sheet 2 m 2 u. r N

N 2 LL.

Q INVENTORS FRANCIS E. GALVIN Y GERALD J. ROFFMAN B 2 4, adzzwoza, cz-J. Q4 Y ATTORNEYS REUSABLE SHIELDED CONTAINER Francis E. Galvin and Gerald J. Rolfman, Philadelphia,

Pa., assignors to the United States of America as represented by the Secretary of the Army Filed May 10, 1960, Ser. No. 28,174 6 Claims. (Cl. 206-46) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a container for transporting an electron discharge tube having an exterior or stray magnetic held. its purpose is to provide an improved container which confines the extraneous magnetic fields to the immediate lvicinity of the tube and protects the tube against injury or deterioration during its transportation. The shielding procedure may be applicable to other magnetron tubes of similar configuration and field strength.

It is known that electron discharge devices, such as large magnetrons, are surrounded by stray magnetic fields. In the air transportation of such devices it is therefore necessary that these fields be isolated from the magnetic compass or sensing device of the aircraft. The present invention provides a proven container which accomplishes this result, is reusable, is suitable for all types of transportation, is water-vaporproof, possesses excellent shock attenuation, and is economical to manufacture. As hereinafter explained, this improved container includes, among other things, a low carbon steeel casing and a low carbon steel interior shield which is suitably spaced from the casing and encloses a resilient material in which the tube is mounted.

The invention Willbe better understood from the 1following description when considered in connection with the accompanying drawings and its scope is indicated by the appended claims.

FIG. 1 is a partial sectional view indicating the relation between the various parts of the magnetically shielded container assembly,

FIG. 2 illustrates the tube as resting upon two of the four non-magnetic molds in which it is supported during its transportation,

FIG. 3 shows how the tube is supported in the interior magnetic shield,

FIG. 4 shows the outside of the interior shield,

FIG. 5 shows the casing lid with the spacing or isolating disk attached,

FIG. 5A is a similar showing of the casing body,

FIG. 6 shows the container with the top coverings of the tube removed,

FIG. 7 differs from FIG. 6 in that the two upper molds are positioned on the tube, and

FIG. 8 differs from FIG. 7 in that the cover of the interior shield is in place.

As indicated by FIG. 1, the container of the present invention includes a casing 10 which has a lid 11 and han-' dles 12. Located within the casing 10-is an interior shield 16 consisting of a wall 13, a bottom 14 and a top 15. The

interior shield 16 is spaced from the casing 10 by an impact cushion ring 17 and impact cushion disks 18 and 19. Mounted within the interior shield 16 are four molds 20, 21, 22 and 23 in which the magnetron 24 rests.

The container is required to restrict the maximum field strength of the packaged tube to a value not greater than 0.00525 gauss at a distance of seven feet from the measuring instrument. The illustrated tube 24 is a magnetron tube type 5795, one magawatt power output, S-band. This is a sensitive and complex electron tube including United States Patent "ice clu-de demagnetization of the tube.

Patented Dec. 18, 1962 two magnets each of which has a field strength of 6000 gausses.

In order to contain or isolate the stray magnetic fields of these magnets, the interior shield 16 is made of low carbon steel having a thickness of .035 inch and conforming to F5 1009 temper 5 of Specification QQ-S-00640 It is a cylindrical container, seam constructed, to preclude welding or riveting. This type of container permits a constant flux flow of extraneous magnetic fields around the circumference of the shield. Heretofore the shielding material has been applied in layers around the inner most box unit. The present shield has the advantage that it is adaptable to normal production practices and can be manufactured at relatively small cost. It is 2.0 inches in diameter, has an inside height of 12 inches, and can be used repetitively thus eliminating re-packaging operations. To prevent corrosion, the steel is prime coated and fin ished with one coat of olive drab enamel.

Consideration has to be given to the spacing between the tube 24 and the shield 16. This is necessary to pre- To maintain the re quired spacing between the tube and .shield, the tube is suspended in the four interchangeable molds 20, 21, 22 and 23 of rubberized curled hair conforming to Specifica, tion MIL-07769. This material consists of 50 percent new stock cattle-tail and winterhog hair and 50 percent repicked hair. The binding elastomer is neoprene, suit,- able for low temperature requirements of --65 F. Molds to 23 are reinforced with imbedded celotex pads in the load bearing area to provide adequate weight distribution of the tube. The cushion molds 20 to 23 are sprayed shock.

During the design and development of the shielded package, it was found that an air void between the interior shield 16 and the casing 10 is essential in ascertaining the thickness of the shield. Tests showed that, for the magnetron tube, type 5795, an average air void of one inch satisfies the need of a single interior shield provided the casing 10 consisted of 16 gauge low carbon steel. The air void is accomplished by the use of the two impact cushion disks 18 and 19 and the impact cushion ring 17 all of which are secured to the outer casing 10 with an adhesive.

The casing 10 is a reusable drum made of low carbon steel conforming to F8 1009, PS 1022, temper number 3, l6 gage of Specification QQ-S-00640. It is provided with handles 12 and with a necked in bottom with reinforced chine. This bottom construction permits stacking and sufiiciently reinforced to preclude the use of rolling hoops. The lid 11 is sealed to the wall 13 by a seal ring 25.

Constructed as described above, the shielded container assembly was subjected to an extraneous magnetic field test, a rough handling test, an altitude test, and an immersion test.

The average stray or extraneous magnetic field at a distance of seven feet from the magnetron was found to be milligausses with no shielding, 13 milligausses with the magnetron mounted within the inner shield, and 2 milligausses with the shielded container completely assembled. These results clearly indicate the effectiveness of the shielded container.

In the rough handling test, the shielded container assembly with a simulated load was dropped cornerwise from a height of 30 inches onto a steel plate, this test being repeated on each quarter of the drum. The instrument used for recording shock was an Imp-act-O-Graph, Model HXS which indicated a maximum reading of 14 G.

In the altitude test, the shielded container assembly was placed in an altitude chamber at ambient temperature and the temperature was reduced to 65 F. The pressure of the chamber was then reduced gradually to simulate an altitude climb of 500 feet per minute. The maximum altitude reached was 40,000 feet. Thereafter the pressure was increased gradually at a rate of about 500 feet per minute to lower the altitude to that of sea level. The container remained tight and there was no apparent distortion during the entire test.

The immersion test was the last to be made. It consisted of immersing the container assembly in water so that the level of the water was one inch above the top of the container. After an immersion of 15 minutes, the container was opened and no evidence of leakage or condensation Within the container was found.

From these tests, it is apparent that the shielded container assembly is capable of (l) reducing the stray magnetic fields to a point where the shielded container meets the stringent requirements of Specifications T.0.00-85A- 16-1 and MIL-S4473 and (2) withstanding rough usage to an extent which renders it reusable.

We claim:

1. A magnetically shielded shipping container assembly for transporting a device having stray magnetic fields capable of affecting instruments in close proximity thereto including: a single cylindrical interior shield of low carbon steel, resilient non-magnetic means for positioning said device within said shield and in spaced relationship therewith, a single closed exterior casing of low carbon steel surrounding said shield, and resilient non-magnetic means maintaining said single shield in spaced relationship with said casing.

2. A shipping container assembly according to claim 1 wherein said non-magnetic means are in the form of rubberized curled hair.

3. A shipping container assembly according to claim 1 wherein the non-magnetic means for positioning the device is in the form of four semicircular molds preformed to have a radial outer surface matching an inner contour of said shield, a substantially radial inner contour to receive said device, a substantially flat transverse surface and a transverse surface provided with an indentation to cooperate with said substantially radial inner contour to receive said device, and said molds assembled so that the device is enclosed by said molds and held in frictional contact therewith while at the same time causing said molds to be in frictional contact with said inner contour of said shield.

4. A shipping container assembly according to claim 1 wherein the non-magnetic means maintaining the shield in spaced relationship with the casing consists of an impact cushion ring affixed to the interior of said casing and impact cushion disks affixed to the top and bottom of said casing.

5. A shipping container assembly according to claim 1 wherein said shield has a thickness of 0.035 inch and is seam constructed to permit a continuous flow of stray flux around its circumference, and wherein said casing is spaced one inch from said shield and consists of 16 gauge low carbon steel.

6. A shipping container assembly according to claim 5 further characterized by said non-magnetic means being in the form of rubberized curled hair, said non-magnetic means for positioning the device being in the form of four semicircular molds preformed to have a radial outer surface matching an inner contour of said shield, a substantially radial inner contour to receive said device, a substantially fiat transverse surface and a transverse surface provided with an indentation to cooperate with said substantially radial inner contour to receive said device, and said molds assembled so that the device is enclosed by said molds and held in frictional contact therewith while at the same time causing said molds to be in frictional contact with said inner contour of said shield, and by said non-magnetic means maintaining the shield in spaced relationship with the casing consisting of an impact cushion ring affixed to the interior of said casing and impact cushion disks aflixed to the top and bottom of said casing, whereby stray magnetic fields emitted from said device having a field strength of 12,000 gausses will be reduced to 2 milligausses at a distance of 7 feet from said shipping container.

References Cited in the file of this patent UNITED STATES PATENTS 2,388,848 Howe Nov. 13, 1945 2,897,959 Gretz Aug. 4, 1959 2,954,140 Sutherland et a1. Sept. 27, 1960 

